The present invention relates to a prober and a probe contact method for connecting an electrode of a die to a tester in order to conduct an electrical inspection of a plurality of semiconductor chips (dies) formed on a semiconductor wafer.
In a semiconductor manufacturing process, a plurality of chips (dies) each having a semiconductor device are formed by subjecting a thin, circular-disk-shaped semiconductor wafer to various processes. After the electrical characteristic of each chip is inspected and the chips are separated with a dicer, each chip is fixed to a lead frame, etc. and assembled. The above-mentioned inspection of the electrical characteristic is conducted using a prober and a tester. The prober fixes a wafer to a stage and causes probes to come into contact with the electrode pads of each chip. The tester supplies power and various test signals from a terminal to be connected to the probe and confirms whether the operation is normal by analyzing the signal output to the electrode of the chip with the tester.
The semiconductor device is used for many purposes and used in a wide temperature range. Because of this, when inspection of a semiconductor device is conducted, it is necessary to conduct the inspection, for example, at room temperature (normal temperature of a room), at a high temperature, such as 200° C., and at a low temperature, such as −55° C., and the prober is required to be capable of conducting inspection in such environments. In order to cope with this, for example, a wafer temperature adjustment mechanism, such as a heater mechanism, chiller mechanism, heat pump mechanism, etc., which changes the temperature of the surface of a wafer stage, is provided under the wafer surface mount of a wafer stage that holds a wafer in a prober and the wafer held on the wafer stage is heated or cooled.
FIG. 1 is a diagram showing a general configuration of a wafer test system comprising a prober having a wafer temperature adjustment mechanism. As shown schematically, a prober 10 has a base 11, a movement base 12 provided thereon, a Y axis movement base 13, an X axis movement base 14, a Z axis movement section 15, a Z axis movement base 16, a θ rotation section 17, a wafer stage 18, a needle positioning camera 19 for detecting the position of a probe, supports 20 and 21, a head stage 22, a wafer alignment camera 23 supported by a support (not shown), a card holder 24 provided on the head stage 22, a probe card 25 to be attached to the card holder 24, and a stage movement control section 27. The probe card 25 is provided with a probe 26 of a cantilever system. The movement base 12, the Y axis movement base 13, the X axis movement base 14, the Z axis movement section 15, the Z axis movement base 16, and the θ rotation section 17 constitute a movement/rotation mechanism that moves and rotates the wafer stage 18 in the directions of the three axes and around the Z axis, which is controlled by the stage movement control section 27. Since the movement/rotation mechanism is widely known, its explanation is omitted here. The probe card 25 has the probe 26 arranged in accordance with the arrangement of the electrodes of a device to be inspected and is exchanged in accordance with a device to be inspected.
In the wafer stage 18, a heater/cooling liquid path 28 for raising or reducing the temperature of the wafer stage 18 is provided. A temperature control section 29 controls the power to be supplied to the heater of the heater/cooling liquid path 28 and the temperature of the cooling liquid to be circulated through the cooling liquid path. Due to this, it is possible to adjust the wafer stage 18 to a desired temperature between high and low temperatures and in accordance with this, it is possible to inspect by adjusting a wafer W held by the wafer stage 18 to a desired temperature. The temperature control section 29 controls the temperature based on the temperature detected by a temperature sensor (not shown), provided near the surface of the wafer stage 11.
A tester 30 has a tester main body 31 and a contact ring 32 provided to the tester main body 31. The probe card 25 is provided with a terminal to be connected to each probe and the contact ring 32 has a spring probe arranged so as to come into contact with the terminal. The tester main body 31 is held by a support mechanism (not shown), with respect to the prober 10.
When inspection is conducted, the Z axis movement base 16 is moved so that the needle positioning camera 19 is located under the probe 26 and the needle positioning camera 19 detects the front end position of the probe 26. The front end position of the probe 26 must be detected whenever the probe card is exchanged with another and this is also done appropriately each time a predetermined number of chips are measured, even if the probe card is not exchanged. Next, in a state in which the wafer W to be inspected is fixed to the wafer stage 18, the Z axis movement base 16 is moved so that the wafer W is located under the wafer alignment camera 23 and the position of the electrode pad of the semiconductor chip on the wafer W is detected. It is not necessary to detect all of the positions of the electrode pads of one chip, but it is required to detect the positions of some of the electrode pads. In addition, it is not necessary to detect the electrode pads of all of the chips on the wafer W, but the positions of the electrode pads of some chips are detected.
FIG. 2 is a diagram explaining the operation of making the electrode pad come into contact with the probe 26. After the position of the probe 26 and the position of the wafer W are detected, the wafer stage 18 is rotated by the θ rotation section 17 so that the direction of arrangement of electrode pads of the chip coincides with the direction of the arrangement of the probes 26. Then, after moving the wafer stage 18 so that the electrode pad of the chip to be inspected of the wafer W is situated under the probe 26, the wafer stage 18 is lifted and the electrode pad comes into contact with the probe 26.
FIG. 3A shows an arrangement example of electrodes 42 on a semiconductor chip (die) 41 formed on the wafer W and FIG. 3B shows an arrangement example of the probes 26. The probes 26 are arranged in accordance with the arrangement of the electrodes 42. In recent years, a multi-probing process, which inspects a plurality of dies simultaneously, has been used in order to improve throughput and the number of probes 26 is equal to the number of electrodes of one die multiplied by the number of dies to be inspected simultaneously.
Accompanying the trend of reduction in size and increase in the level of integration, there is a trend for electrodes to become smaller and smaller, and an electrode about the size of 30×30 μm has been made recently. In order to cope with this, it is necessary to improve the positional precision of the probe 26 and further, it is necessary to improve alignment.
When the wafer W is inspected at a high or low temperature, or when the wafer W is inspected at room temperature after inspection at a high or low temperature is finished, the temperature control section 29 controls the wafer stage 18 so that it reaches a desired inspection temperature after the wafer W is fixed to thereto. When the temperature of the wafer stage 18 reaches the desired range of inspection temperatures, the temperature of the wafer W is assumed to be within the range of desired inspection temperatures, and the interrelation (relative position) between the front end position of the probe 26 and the electrode position of the die of the wafer W is detected by means of alignment, and after the electrode of the die is moved to immediately under the probe 26 based on the detected relative position, it is raised and comes into contact therewith. When the inspection of the die in contact with the probe is finished, after the wafer W is lowered and the electrode is separated from the probe 26, the electrode of the die to be inspected next time is moved to immediately under the probe 26 and is then raised and comes into contact therewith. Such an operation is repeated until the inspection of all of the dies of the wafer W is finished.
As described above, the wafer stage 18 is provided with a heater/cooling liquid path 28 and the temperature of the wafer stage 18 is forcibly changed. Therefore, it is possible to change the temperature at a comparatively high rate. When the temperature of the wafer stage 18 reaches a desired inspection temperature, the temperature control section 29 maintains the temperature during inspection. On the other hand, since no temperature adjustment mechanism is provided at each portion of, for example, the card holder 24, probe card 25, and movement mechanism, except for the wafer stage 18, there is a difference in temperature from the wafer stage 18 the temperature of which is adjusted, and the temperature gradually changes nearer the temperature of the wafer stage 18 even during inspection. This change is great in the card holder 24 and the probe card 25 near the wafer stage 18 and comparatively little in the movement mechanism.
As described above, since the temperature of the portions other than the wafer stage 18 also changes after alignment processing has been performed, the relative position between the probe 26 detected by the alignment processing and the electrode of the die of the wafer W also changes due to the thermal expansion of each portion. Because of this, if other dies not inspected yet, are moved for inspection after the inspection of part of the dies of the wafer is finished, the probe may not come into contact with the electrode properly.
If the shape of the electrode is large and the allowable range of the contact position of the probe is large, there will be no problem even if the above-mentioned relative position changes, however, as described above, the size of the electrode has become smaller and smaller in recent years, and the allowable range of the contact position of the probe has also become smaller, so the frequency of probing errors cannot be ignored.
In order to avoid such a problem, it is suggested to measure the change in the relative position between the wafer alignment camera 23 and the probe card 25, and the change in the amount of movement of the wafer stage 18 (the change in the distance between the position of the wafer alignment camera 23 and the probing position), etc., using a precision laser length measuring machine to compensate for the amount of movement. However, a laser length measuring machine is very expensive and if many machines are used, cost will be considerable.
Because of this, alignment should be carried out after the temperatures of the portions other than the wafer stage 18 become stable, allowing a sufficient standby time after the wafer stage 18 has reached a predetermined inspection temperature. However, since the temperature adjustment mechanism is not provided for portions other than the wafer stage 18, the temperatures of the other portions take some time to become stable, and throughput is reduced remarkably.
Further, it has been carried out that the alignment is performed after the wafer stage 18 has reached a predetermined inspection temperature, the inspection is then started, and a correct relative position is detected by repeating the alignment operation at short cycles. However, in order to carry out the alignment operation, it is necessary to move the wafer stage to under the alignment camera 23, and it is also necessary to perform image processing to detect the position of the electrode, and thus a certain amount of time is required, which directly leads to a reduction in throughput. In addition, the detection of the position of the probe 26 will also cause throughput to further reduce.